Head First Servlets and JSP, 2nd Edition

You can’t do ${foo.1}

With beans and Maps, you can use the dot operator, but only if the thing you type after the dot is a legal Java identifer.

This

${musicMap.Ambient}

Note

works

Is the same as this1

${musicMap["Ambient"]}

Note

works

But this

${musicList["1"]}

CANNOT be turned into this

${musicList.1}

Note

NO! NO! NO!

Note

If you wouldn’t use it for a variable name in your Java code, DON’T put it after the dot.

Sharpen your pencil

What prints?

Given the servlet code below, figure out what would print (or if there’d be an error, just write, you know, “error”). Answers are at the bottom of the next page.

java.util.ArrayList nums = new java.util.ArrayList();
nums.add("1");
nums.add("2");
nums.add("3");
request.setAttribute("numbers", nums);
String[] favoriteMusic = {"Zero 7", "Tahiti 80", "BT", "Frou Frou"};
request.setAttribute("musicList", favoriteMusic);

1. ${musicList[numbers[0]]}

2. 

3. ${musicList[numbers["2"]]}

4. ${musicList[numbers[numbers[1]]]}

Code Magnets

Don’t be surprised if you find something like this on the exam (except in the real exam it’ll look... uglier).

Study the three classes on the page, and the servlet code on the opposite page, then construct the code magnets to make the EL that’ll produce the response shown in the browser. (Turn the page for the answers, but not until you DO THIS, especially if you’re going to take the exam.)

foo.Toy

package foo; public class Toy { private String name; public void ...